Various balloon catheter designs have been developed for use in a wide range of medical catheterization procedures. Such catheterization procedures include angioplasty dilatation, stent delivery, and localized drug delivery.
Balloon catheters for angioplasty dilatation generally comprise an elongated catheter tube having proximal and distal ends, and an expandable balloon located at the distal end of the catheter tube. The catheter tube includes one or more lumens extending longitudinally throughout essentially the entire length of the tube. In its basic form, at least one of the lumens functions as a conduit for the flow of inflation fluid from the proximal end of the catheter tube to the interior of the balloon. When it is desired to inflate the balloon, pressurized inflation fluid is injected into the proximal end of the inflation lumen via a syringe or other pressure infusion device.
Balloon dilatation catheters are frequently used to dilate blood vessels restricted by an atherosclerotic lesion or stenosis. To this end, a balloon dilatation catheter is introduced into a patient's vascular system such that the dilatation balloon is positioned across the area of a narrowing. Inflation fluid is then injected through the catheter tube lumen and into the balloon. The balloon expands to press against and open the narrowed portion of the blood vessel.
The success of such a dilatation procedure largely depends on the proper inflation of the balloon, thus requiring great skill on the part of the administering physician. Should the physician provide too little pressure in injecting the inflation fluid into the catheter, the balloon will not inflate to the extent necessary and the dilatation will be insufficient. However, should the physician inject the inflation fluid into the catheter at too great of a pressure, the balloon will over-inflate thereby creating the danger of trauma to the blood vessel wall. Moreover, should the inflation fluid be injected at an excessively high pressure level, the balloon may burst.
As identified above, another balloon catheter procedure involves the delivery of a stent within a patient's vasculature. Stent delivery procedures are commonly employed in conjunction with angioplasty dilatation procedures, such as the one described above for treatment of a stenosis. It has been found that a stenosis is susceptible to collapse or restenosis following an angioplasty dilatation procedure. Thus, such angioplasty dilatation procedures are frequently followed by the implantation of a stent to prevent collapse of the stenosis or restenosis. During such a stent delivery procedure, the stenosis is opened as described above with a dilatation balloon catheter. Next, a stent, having a reduced outer diameter and carried about an expansion balloon, is positioned within the opened stenosis. Then, the expansion balloon is inflated with pressurized fluid to expand the outer diameter of the stent into engagement with the stenosis. It will be understood that because an expansion balloon is inflated with pressurized fluid to implant the stent at the stenosis, the same problems described above with regard to the proper inflation of a dilatation balloon also apply to the inflation of an expansion balloon for a stent delivery catheter. Namely, if the balloon is under-inflated, the stent may not be properly implanted. Conversely, if the balloon is over-inflated, the stent may cause trauma to the vessel walls or the balloon may burst.
Further, recent balloon catheter designs have been developed for treatment of a stenosis using a single catheter device enabling both balloon dilatation and stent delivery. To this end, such balloon catheters generally comprise a catheter tube having at least two balloons located proximate its distal end. According to this design, one of the balloons functions as a dilatation balloon and another functions as an expansion balloon which carries a crimped stent. Thus, the combined dilatation/stent delivery procedure is performed by the administering physician through the use of only one catheter device, and not separate angioplasty dilatation and stent delivery catheters. However, the above-identified problems with regard to the difficulties in properly inflating the dilatation and stent expansion balloons remain. Indeed, these problems are compounded to the extent that there are two or more balloons which must be inflated. Further complicating the balloon inflation procedure is that different inflation pressures may be required for each of the balloons.
Moreover, other stent delivery balloon catheter designs have been developed for delivering and implanting bifurcated or Y-shaped stents to a bifurcated vessel within a patient's vasculature. Generally, such stent delivery balloon catheter designs consist of an elongated catheter tube having two separate distal ends, each of which includes an inflation balloon. Further, based on the respective sizes of the branched vessels of the treatment site, the balloon sizes may vary. In practice, a bifurcated stent is crimped into the dual balloons to obtain a low profile to allow for passage through the patient's vasculature. The dual balloon catheter and crimped stent are advanced over guide wires to the bifurcated vessel treatment site. The balloons are then inflated to expand and secure the Y-shaped stent to the bifurcated vessel. In addition to the problems described above with properly inflating a multiple balloon catheter, bifurcated stent delivery balloon catheters present problems associated with the simultaneous inflation of multiple balloons. For example, the simultaneous inflation of multiple balloons typically involves the use of multiple sources of pressurized inflation fluid requiring the participation of more than one person. This is particularly the case when different sized balloons are used, as the inflation fluid must be injected into the various balloons at different pressure levels.
A third category of balloon catheters is drug delivery catheters. Various drug delivery catheter designs and procedures have been developed for the delivery of therapeutic and/or diagnostic agents to a specific site within a patient's vasculature or bodily organ. Typically, such drug delivery catheter designs include a balloon having a plurality of apertures spaced about its surface located at the distal end of a catheter tube. The interior of the balloon is in fluid communication with an inflation lumen which extends throughout the length of the catheter tube. After the balloon has been positioned within the patient's vasculature or other bodily organ at the treatment site, inflation fluid comprising a therapeutic or diagnostic agent is injected under pressure through the inflation lumen and into the balloon. The balloon expands under the pressure of the inflation fluid and presses against the body wall at the treatment site. The pressurized inflation fluid then migrates through the apertures in the balloon wall and penetrates the tissue wall at the treatment site. The balloon apertures are sized such that the balloon remains pressure-inflated despite the flow of the fluid agent through the apertures of the balloon wall.
Perforated balloon drug delivery catheters such as the one described above are capable of delivering a wide range of therapeutic and/or diagnostic agents. For example, perforated balloon catheters are designed for use in conjunction with angioplasty dilatation for treating the site of an opened atherosclerotic lesion or stenosis with a therapeutic agent such as heparin to inhibit unregulated smooth muscle cell proliferation and prevent restenosis. Alternatively, perforated balloon catheters may be used to deliver a drug or agent to dissolve a stenosis in an effort to avoid use of angioplasty or atherectomy procedures, or to deliver a thrombolytic agent to dissolve a clot at the lesion site. In addition, perforated balloon catheters may also be used to administer antibiotics or anesthetics directly to the treatment site prior to removal of the catheter. Other agents which may be administered through perforated balloon catheters include steroids for suppressing inflammation in a localized tissue site, anti-neoplastic for treating a tumor site, chemotherapeutics or any desired mixture of individual pharmaceuticals.
However, despite the development of this broad range of applications for perforated balloon drug delivery catheters, improvement in the control of the infusion of the inflation fluid to the treatment site is desirable. Typically, the inflation fluid is manually injected into the drug delivery balloon catheter by means of a syringe device comprising a syringe barrel and plunger. Accordingly, the rate of infusion of the inflation fluid and pressurization of the balloon depends on the pressure applied on the syringe plunger by the administering physician. It has been found that the precise control of the pressure and rate at which the inflation fluid is injected into the catheter is important, requiring great skill on the part of the administering physician. For example, the exertion of excessive pressure on the syringe plunger by the physician may result in over-pressurization of the inflation fluid within the balloon, such over-pressurization may cause high velocity jetting of the inflation fluid through the balloon apertures and possible trauma to the interior walls of the patient's vasculature.
Moreover, with regard to each of the above-described balloon catheters, it has been found that the use of a pressure gauge to assist the physician does not assure precise control of the pressure at which the inflation fluid is injected into a balloon catheter. For example, a drop in the pressure indicated on the pressure gauge generally causes the physician to accelerate the movement of the syringe plunger into the syringe barrel, thereby resulting in a pressure spike. Any such pressure spike may result in over-pressurization of the balloon and, consequently, over-inflation of an expansion balloon or possible high velocity jetting of inflation fluid through the apertures of a drug delivery balloon.
Thus, there presently exists a compelling and recognized need for a valve apparatus which provides a safe and reliable means for limiting the pressure of inflation fluid introduced into a balloon catheter.
It is, therefore, a principal object of the present invention to provide an apparatus for limiting the pressure of inflation fluid introduced into one or more balloons associated with at least one catheter device.
It is a further object of the present invention to provide an apparatus which may be selectively adjusted to provide different cut-off pressures for the inflation fluid injected in separate balloons of a balloon catheter.
It is a further object of the present invention to provide an apparatus which enables the use of a single source of pressurized fluid for the controlled inflation of a plurality of balloons associated with one or more balloon catheters.
It is a further object of the present invention to provide an apparatus which enables simultaneous inflation of a plurality of balloons associated with one or more balloon catheters.
It is a further object of the present invention to provide an apparatus for use in a drug delivery balloon catheter to limit the pressure of inflation fluid introduced into a perforated balloon and prevent high velocity jetting of inflation fluid through the apertures of the balloon wall.
It is a further object of the present invention to provide an apparatus for use with a drug delivery balloon catheter which may be selectively adjusted to provide different cut-off pressures to accommodate the specific flow characteristics of a variety of therapeutic and/or diagnostic agents.
Objects and advantages of the invention are set forth in part above and in part below. In addition, these and other objects and advantages of the invention will become apparent herefrom, or may be appreciated by practice with the invention, the same being realized and attained by means of instrumentalities, combinations and methods pointed out in the appended claims. Accordingly, the present invention resides in the novel parts, constructions, arrangements, improvements, methods and steps herein shown and described.